A conventional ring-type voltage-controlled oscillator in general comprises amplifier elements of number N (N is an odd number) which can change a delay time established between input and output by a signal input from a delay-time control terminal and have input and output terminals and function as an inverting amplifier, wherein the respective input and output terminals are connected in the form of a ring.
However, the conventional voltage-controlled oscillator has a problem that it trends to bring the dispersed quality of the delay time in the amplifier elements and a relatively high temporal fluctuation of the output clock, i.e., jittering, due to dispersed quality in devices that comprise the voltage-controlled oscillator, changes in operation environment caused by changes in voltage of power supply or the like, the noise induced from outside and the like. In particular, since a fluctuation in phase difference between output clocks occur when obtaining an output clock from two or more output clock terminals, it is necessary for a system that makes a timing for a synchronization circuit by a voltage-controlled oscillator to be designed with having a margin for such fluctuation.